This invention relates to molding presses, and more particularly to mechanism for opening and closing the molds of a molding press.
In transfer and injection molding of synthetic thermosetting and thermoplastic resins, rubber and other elastomers, die cast and other materials, the presses must furnish a clamping force greater than the force created by the transferring or injecting of materials into the closed mold. The created force depends upon the size of the mold, the number of mold cavities, the material being transferred or injected and the transfer or injection pressure being used. These pressures created within the mold, trying to force it open, vary from a few tons to several thousand tons.
Pressures of these magnitudes have been accommodated in molding presses heretofore by mold closing mechanisms the structures of which present certain limitations and disadvantages. Typical of these prior structures is a molding press in which the movable mold platen is moved between open and closed position by toggle joints operated by a piston-cylinder unit and pivotally interconnecting a fixed base and a movable pancake cylinder support plate. A pancake type clamping cylinder interengages its support plate and the movable mold platen to provide final high pressure for closing the mold. This structural arrangement seriously limits the extent of opening of the mold, thereby rendering difficult and more time consuming the clearing and maintenance of the mold sections. It also requires the piston-cylinder unit for the toggle joints to provide considerable power, and therefore the closing movement of the mold is correspondingly slowed. This is reflected in a longer molding cycle.